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Jeep Grand Cherokee A/C Heating Ventilation

371 messages,  Last post on Oct 27, 2009 at 2:04 PM

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What is this discussion about? Jeep Grand Cherokee, Heating / Cooling, SUV

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#314 of 371 2003 GC Temperature Control Rotary Knob by machinist1 Apr 17, 2009 (9:23 am)
My 2003 apperars to have a bad temperature control rotary knob. (This vehicle does not have dual-zone control). I usaully get a blend of hot/cold air regardless of where I have the knob set. However, if I press on the knob or jimmy it a bit, the damper will move and air will be supplied at the desired temperature. Fan blower, mode selector, heater and AC all work fine...this is just a temp control issue...   I've been reading this forum a while, but I have not seen a post describing a similar problem. Has anyone else experienced this, and what is the difficulty and $ of replacing this control?
#315 of 371 HeaterTreater by heatertreater Apr 17, 2009 (11:21 am)
The knob may be slipping and you will have to remove it and see if the connection is cracked. This happens a lot on the Ford F150's, but I'm surprised on the GC. It's just a variable resistance switch that the knob is turning and there shouldn't be enough resistance to strip the knob unless someone is trying to turn it past the end points.   You can fully open the glove box and examine the actuator motor to the left of the glove box opening. When you turn the temp knob, the motor should move. The system is under computer control and will shut that motor down when it detects a system fault, so failure of the motor to turn does not necessarily mean a bad motor.   The motor can be removed by removing two philips screws and pulling the motor straight back. Examine the motor connection and blend door axle to see if there is damage. The white axle going into the plenum box has a limit pin extending radially from the axle that is constrained between two stop points molded into the plenum box. Check that the limit pin is not broken and that you can turn the blend door axle easily with your fingers. You should be able to manually switch between heat and no heat with your fingers. You can check the motor with a 9V battery and a snap connector. Just touch the wires to the two terminals and the motor should turn, and reverse when you switch the wires.   From your description, I'd be concerned with checking the knob closely. If the connection is cracked, you should feel a "bump" in the knob when you turn it. This would be a sign of a cracked connector that is not engaging the switch. You should also be able to feel an end point to movement. If the knob spins 360 degrees, the connection is broken. If nothing else, remove the knob and use a pair of pliers... Just kidding, a broken knob should be easy to fix with epoxy and a couple of loops of wire around the knob connection.
#316 of 371 2003 Grand Cheorekee with A/C and Heat problems by matthewbowes86 Apr 21, 2009 (11:29 am)
Hey, I have a 2003 Jeep Grand Cheorekee Limited and for awhile now I havn't had heat but the a/c worked fine. But lately my a/c only works when driving fast. The faster I drive the more cool air comes out but when I'm idlle, nothing comes out. I can't control the air ither, if I drive fast the a/c is blowing fast and I can't turn it lower it blows fast if its on and I'm driving fast (50 mph +). I was wondering what the problem could be. Replies to this message: heatertreater (Apr 22, 2009 7:39 pm) blendor (Apr 23, 2009 6:21 am)
#320 of 371 2003 Grand Cheorekee with A/C and Heat problem [matthewbowes86] by heatertreater Apr 22, 2009 (7:39 pm)
Replying to: matthewbowes86 (Apr 21, 2009 11:29 am) This sounds like a problem with the re-circ door. This door has two positions, block external intake vent forcing air to be pulled in from the internal vent, and block internal vent forcing air to be pulled in from the external vent. When the door breaks, it can fall down or hang in the center position leaving both the external vent and internal vent open. At highway speeds, air will flow into the external vent and out of the internal vent...like having a window rolled down all the time. In your case, it sounds like the door may be broken and has fallen down and is partially blocking air intake to the fan motor. You can see the intake port behind the glove box or run another simple test. With the fan on full blast, check the air flow into the external vent between the hood and windshield. With re-circ off, you should feel air being pulled into the vent, and the flow should stop with re-circ on. There are aftermarket repairs to address and fix the re-circ door and a video on youtube.   HeaterTreater
#321 of 371 Re: 2003 Grand Cheorekee with A/C and Heat problems [matthewbowes86] by blendor Apr 23, 2009 (6:21 am)
Replying to: matthewbowes86 (Apr 21, 2009 11:29 am) Giving your symptoms is only a part of the diagnosing process.   The 99/04 Jeep GC Limited has a fault code system you can read. The fault code system is an excellent place to start the diagnosing process.   Since you have the Automatic Zone Control system (AZC) The first thing you should do is check the AZC fault codes.   To read the fault codes: 1. Turn on the ignition switch. 2. Turn on the AZC system. The temperature settings should be displayed for both sides. 3. Simultaneously hold down the AC and the Re-Circ buttons. 4. Then turn the driver’s side temperature (Left) control knob to the right (CW) one click. 5. Then release the AC and Re-Circ buttons.   If there are no fault codes, the “00” display value will remain in the window. If there are any codes, each will be displayed for one second in ascending numerical sequence. Once all codes have been displayed, the system will repeat the fault code numbers. This will continue until stop the process by moving the left side set temperature control one click in either direction, by pressing both the A/C and Recirc buttons at the same time, or the ignition is turned off.   Record all of the fault codes and also describe any symptoms you are having with your heating system. Like - Are you getting a good air flow thru your vent outlets? Can you direct the air flow to the different outlet vents?   Post your fault codes and symptoms. I’ll interpret them for you and advise you on how you could repair your heating system.     Blen Dor
#322 of 371 Jeep Grand Cherokee Heater AC by heatertreater Apr 24, 2009 (3:05 pm)
Certainly reading the codes is not going to hurt anything, but you already have most of the information that you need. Assuming that the heater lines are getting hot and the fan is blowing, lack of heat on either or both sides of the GC is a 99.9% indication of a broken blend door. The problem is pervasive on the GC and almost a knee jerk diagnosis. Reading the code and getting a 54 and/or 56 will take you from 99.9% to 100%   Virtually every GC in your year range is going to throw a 52 code for re-circ door travel too large. The re-circ door is larger and stronger than the blend doors and will "bend" before it breaks. The computer system will detect that the movement is out of spec, but this doesn't necessarily indicate that it is broken. It WILL break over time once you see the 52 code, but it can go another year or so with perfectly normal operation even with the code. The physical examination tests that I posted in the previous answer will tell you definitively what's going on with the re-circ door. The code will only alert you that the door is in the process of breaking and could possibly be broken already. I'd suggest that you just skip the re-circ door code and go straight to physical examination. Guys trying to sell you something based on just reading codes are either uniformed or scamsters.   HeaterTreater Replies to this message: matthewbowes86 (Apr 24, 2009 5:24 pm) blendor (Apr 27, 2009 4:35 pm) matthewbowes86 (Apr 24, 2009 5:26 pm)
#323 of 371 Re: Jeep Grand Cherokee Heater AC [heatertreater] by matthewbowes86 Apr 24, 2009 (5:24 pm)
Replying to: heatertreater (Apr 24, 2009 3:05 pm) Thanks for the advice. I did the fault code process and got 52, 54 and 56. Replies to this message: blendor (Apr 27, 2009 4:35 pm)

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